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Engine Cranks But Won't Start

Frustrated by an engine that cranks but won't start? Well, that's the topic of this installment of our Diagnostics Kept Simple series.

Frustrated by an engine
that cranks but won't start? Well, that's the topic of this installment
of our Diagnostics Kept Simple series. We'll walk you through simple diagnostic
procedures, step-by-step, that will enable you to find the problem and
fix it fast. When an engine cranks but won't start, the problem can usually
be traced to one of three possibilities-the ignition system, the fuel
supply system or engine mechanical problems. Before beginning the elimination
process, however, you'll always want to check for any no-start-related
diagnostic trouble codes (DTCs). Testing of the ignition system will include
a spark output check, as well as looking for problems with plug wires,
ignition modules and triggers. Proper test gear here is a must. Testing
the fuel supply system will take a little more time, but problems there
account for a considerable share of no-starts.

Also, don't overlook
engine mechanical problems, such as low compression, a jumped timing chain
or belt or a plugged exhaust. To help narrow down the possibilities and
get to the root of the problem faster, always ask the customer the recent
history of the vehicle. There may have been a particular event that caused
or contributed to the no-start. You may be surprised by the responses
you get from customers when you question them about the particulars surrounding
their vehicle. Always ask if any work has been performed on the vehicle
recently. When did they first notice the problem? Did the engine sputter
or stall before it refused to start? Have there been any changes in fueling
patterns-different types of fuel or places of purchase? Was the tank run
dry? Is there a security system installed on the vehicle? Has the no-start
condition ever happened before? The tear-out flowchart that follows takes
you through step-by-step diagnostic procedures for a typical engine. Of
course, you'll want to refer to your repair manuals or other reference
materials that deal with the specific make and model you're working on
for component testing and replacement procedures. Use the easy-to-follow
three-hole-punched chart starting on the next page to isolate the no-start
problem and fix it fast. Keep it handy for future use. Note: If the tear-out
flowchart is missing, circle #24 on the Product Information Card on page
77.